Aromatic compounds

ABSTRACT

A process for the preparation of novel compounds with a tetraline-type structure, which are useful as perfuming ingredients, is described.

This application is a division of U.S. patent application Ser. No.08/195,803 filed Feb. 14, 1994, now U.S. Pat. No. 5,442,124, which is acontinuation-in-part of U.S. patent application Ser. No. 07/911,447,filed Jul. 10, 1992, now U.S. Pat. No. 5,324,875, which is a division ofU.S. patent application Ser. No. 07/544,285, filed Jun. 26, 1990, nowU.S. Pat. No. 5,162,588.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to organic synthesis and, in particular tothe preparation of novel compounds which are useful perfumingingredients. It relates to a process for the preparation of a compoundof formula ##STR1## wherein a) indexes m and n are identical and standeach for an integer number equal to zero, symbols R¹ and R² areidentical and represent each a hydrogen atom, or are different andrepresent each a hydrogen atom or a methyl radical, symbols R⁵ and R⁸stand each for a methyl radical, symbols R⁶ and R⁷ can be identical ordifferent and designate each a hydrogen atom or a methyl radical and,either symbol R⁴ represents a methyl radical and symbol R³ stands for ahydrogen atom or a methyl radical, or symbols R³ and R⁴ represent each amethylene radical belonging to a ring such as indicated by the dottedline, with the proviso that the following combinations are excluded:

1. R¹ ═R² ═R³ ═R⁶ ═R⁷ ═H, or

2. R¹ ═R² ═R³ ═H and R⁶ or R⁷ ═CH₃, or

3. R² ═CH₃ and R³ ═R⁶ ═R⁷ ═H, or

4. R² ═CH₃ and R³ ═H and R⁶ or R⁷ ═CH₃, or

5. R¹ ═R³ ═CH₃, or

6. R³ ═R⁴ ═CH₂ and R⁶ or R⁷ ═CH₃ ;

or wherein

b) indexes m and n are different and define each an integer number equalto 0 or 1, symbol R² stands for a hydrogen atom or a methyl radical,symbols R¹ and R³ designate each a hydrogen atom, symbol R⁴ represents amethyl radical and, either symbols R⁵ and R⁶ are identical (n=1) andrepresent each a methylene radical belonging to a ring such as indicatedby the dotted line, R⁷ representing a hydrogen atom and R⁸ a methylradical, or symbol R⁵ stands for a methyl radical and symbol R⁶ for ahydrogen atom, R⁷ and R⁸ being then identical (m=1) and designating eacha methylene radical belonging to a ring such as indicated by the dottedline;

or of a mixture of two or more structural isomers of formula (D, saidprocess comprising:

A. a) the reaction, under the action of light, of a compound of formula##STR2##

wherein symbols R³, R⁶ and R⁷ can be identical or different andrepresent each a hydrogen atom or a methyl radical,

with a halogenation agent to obtain a mixture of halides of formula##STR3## wherein symbols R⁶ and R⁷ are defined as above, symbol R³stands for a hydrogen atom, a halogen atom (X¹ ═X² ═CH₃) or a methylradical, and symbols X¹ and X² are identical and designate each a methylradical (R³ ═halogen) or are different (R³ ═H, CH₃) and represent each ahalogen atom or a methyl radical;

b) the hydrolysis of said mixture of halides to obtain a mixture ofcorresponding alcohols, and the subsequent oxidation of the lattermixture to provide a mixture of aldehydes of formula ##STR4## whereinsymbols R⁶ and R⁷ are defined as above, symbol R³ represents a hydrogenatom or a methyl radical, or a CHO group when Z¹ ═Z² ═CH₃ and symbols Z¹and Z² are identical and designate each a methyl radical when R³ ═CHO,or are different and represent each a CHO group or a methyl radical whenR³ ═H or CH₃ ; and

c) the separation of said aldehydes from the reaction mixture, followedby the treatment of said aldehydes successively with MeLi or MeMgX(Me═CH₃, X═halogen), H₂ O and an oxidation agent, to obtain ketones offormula ##STR5## wherein symbols R⁶ and R⁷ are defined as above, symbolR³ represents a hydrogen atom, a methyl radical or a CH₃ CO group (Z¹'═Z² '═CH₃), and symbols Z^(1') and Z^(2') are identical and designateeach a methyl radical (R³ ═CH₃ CO) or are different and represent each aCH₃ CO group or a methyl radical (R³ ═H, CH₃); or

B. a) the reaction of a compound of formula ##STR6##

wherein symbols R and R³ are different and represent each a hydrogenatom or a methyl radical and symbols R⁶ and R⁷ are defined as above,

with an oxidation or formylation agent to obtain an aldehyde of formula##STR7##

wherein symbol R³ represents a hydrogen atom or a methyl radical;

and

b) the treatment of aldehyde (Ic) with MeI or a Grignard reagentfollowed by a hydrolysis and an oxidation to obtain a ketone of formula##STR8##

wherein symbols R³, R⁶ and R⁷ designate each a hydrogen atom or a methylradical;

or

C. the reaction of a compound of formula ##STR9##

or of a mixture of compounds of formula ##STR10##

wherein symbols R' and R" are different and represent each a hydrogenatom or a methyl radical,

with Cl₂ CHOCH₃, under the Friedel-Crafts acylation reaction conditions,to obtain respectively an aldehyde of formula ##STR11## or a mixture ofaldehydes of formula ##STR12##

wherein symbols Z³ and Z⁴ are different and represent each a CHO groupor a methyl radical;

or with acetyl chloride, in the presence of a Lewis acid, to obtainrespectively a ketone of formula ##STR13## or a mixture of ketones offormula ##STR14##

wherein symbols Z^(3') and Z^(4') are different and designate each a CH₃CO group or a methyl radical.

The invention further relates to a compound chosen in the group formedof:

a. 6-dimethoxymethyl-1,2,3,4-tetrahydro-1,1,2,3,4,4,7-heptamethylnaphthalene;

b. cis-6-dimethoxymethyl-1,2,3,4-tetrahydro-1,1,2,3,4,4,7-heptamethylnaphthalene;

c. trans-6-dimethoxymethyl-1,2,3,4-tetrahydro-1,1,2,3,4,4,7-heptamethylnaphthalene.

BACKGROUND OF THE INVENTION

The search for novel compounds with a musky odor has increased steadilyin the last few years, as a result of the privileged position that thistype of fragrant compounds occupies in modern perfumery. Severalhundreds of these compounds are known today, forming a rich source ofstructural information which has lead certain authors to establishqualitative males intended for predicting which types of chemicalstructures are more likely to provide good quality musky compounds,judging from the intensity, the tenacity or the elegance andindividuality of their odor note. Although these rules can prove helpfulfor finding a few more or less interesting compounds, they do notconstitute an ersatz for the researcher's inventive mind, which revealsitself all the more pertinent when it follows, by intuition, a discoverypath that would have been discouraged by said principles built on thebasis of the known prior art. As it will become apparent shortly, thepresent invention is just an example of this.

It is generally accepted that, in musky aromatic compounds whose benzenering possesses an acyl group substituent, sterical hindrance of thisfunctional group can lead to loss of odor [see, for example, M. J.Beets, Structure-Activity Relationships in Human Chemoreception, 207,ASP Ltd. London (1978)]. Thus, any attempt to further substitute thebenzene ring in the following basic structural skeleton for the aromaticcompounds of interest ##STR15## would have been discouraged from thestart. There are several musky compounds already known which obey thisbasic structure, the best known representative thereof being Tonalid®(origin: Polak's Frutal Works Inc.), which has the following structure##STR16## and is well appreciated in the perfume industry.

Unlike what could have been expected from prior art predictions, we havenow discovered that further methyl and methylene groups can beincorporated in position a or b (see skeleton above) of the benzene ringwithout observing any prejudicial effect on the odor properties of theresulting compounds, in spite of the ensuing perturbation of thefunctional group's environment. On the contrary, several excellent novelmusky compounds have thus been discovered.

THE INVENTION

The present invention provides an original process, as described above,which makes it possible to prepare compounds (I).

We have discovered that compounds (I) possess very interesting odorproperties and that they can be used for the preparation of perfumingcompositions and perfumed articles. As a result of the richness andquality of their musky odor notes, they are particularly suited to thepreparation of perfuming bases and concentrates intended for masculinetype perfumes and Colognes, as well as shaving lotions. In addition,they are equally appreciated for perfuming soaps, shower and bath gels,shampoos and hair care products, cosmetic preparations and bodydeodorants. Furthermore, their use in detergents and fabric softeners isespecially advantageous, since the excellent substantivity of theirmusky odor note ensures an efficient perfuming of the textiles treatedwith these products, which is also longlasting.

As it has already been pointed out, in view of the prior art, the highquality of the odor notes exhibited by these compounds was totallyunexpected. Furthermore, we were also surprised to find that theincorporation of methyl and methylene groups in positions c and/or d ofthe benzene ring in the same basic structural skeleton above-mentioned,eventually simultaneous with the substitution in positions a and b,could lead to novel aromatic musky compounds of formula (I) possessingtruly remarkable odor properties.

We observed, in fact, that the incorporation of additional methyl andmethylene groups in the basic structural skeleton of this type offragrant compounds does not seem to cause substantial modification inthe overall shape of the molecule, unlike what could have beenpredicted, and leads to more or less spherical structures, highly denseand of improved lipophilicity, which turn out to be remarkably powerfulmusky compounds, whose fragrance is stronger than that of the prior artcompounds. This, in turn, means that multiple alkyl or alkenylsubstitution of the basic skeleton, namely in the lipophilic part of themolecule (positions c and d), can cause strong and quite advantageouschanges in the organoleptic properties of these fragrant compounds, anobservation that had not been sufficiently recognized up to now.

A particularly interesting example is that of the compounds having theformula ##STR17## wherein R² designates a hydrogen atom or a methylgroup. The two compounds obeying this formula possess quite distinctodor notes, which are also stronger than that of Tonalid®.

The aldehydic compound of formula (II) is characterized by amusky-amber-animal note reminiscent of natural musk. It furtherpossesses an earthy note resembling that of Cashmeran(6,7-dihydro-1,1,2,3,3-pentamethyl-4(5H)-indanone; origin: InternationalFlavors & Fragrances Inc.) but which is much more powerful than thelatter. In addition, the fragrance of this compound also shows an aspectcharacteristic of the nitro-aromatic musky compounds which renders saidcompound all the more interesting, in view of the fact thatnitro-aromatic musks are gradually disappearing from the perfumer'spalette. It is not only a powerful odor note, far superior to the notesof the musky compounds already available on the market, but also atenacious and substantive note.

As for the ketone compound (II), it develops a quite differentfragrance, showing practically none of the earthy-rooty character foundin its aldehydic homologue cited above and possessing instead a finer,more classical and slightly animal musky note, devoid of the ambercharacter. Although its odor note is less powerful than that of thealdehyde, it is still comparable, in strength, to those of the bestmusky compounds available on the market, while having a differentcharacter.

These two compounds of formula (II), or5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthalenecarbaldehydeand(5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthyl)-1-ethanone,can assume two isomeric forms, i.e., cis and trans. In the case of thealdehyde, these two forms have been separated by gas chromatography andevaluated individually. As for the ketone homologue, only the transisomer could be separated from the mixture containing both isomers.These isomer mixtures directly obtained from the synthesis of compounds(D are also quite excellent odoriferous compounds and can be useddirectly for the preparation of perfuming compositions and perfumedproducts.

Other preferred compounds include:

a) 5,6,7,8-tetrahydro-1,3,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde

b) 5,6,7,8-tetrahydro-3,4,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde

c)5,6,7,8-tetrahydro-1,3,5,5,6,8,8-heptamethyl-2-naphthalenecarbaldehyde

d)5,6,7,8-tetrahydro-3,4,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

e)5,6,7,8-tetrahydro-1,3,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

f)5,6,7,8-tetrahydro-3,4,5,5,6,8,8-heptamethyl-2-naphthalenecarbaldehyde

g)1,2,6,7,8,8a-hexahydro-3,6,6,8a-tetramethyl-4-acenaphthylenecarbaldehyde

h) (1,2,6,7,8,8a-hexahydro-3,6,6,8a-tetramethyl-4-acenaphthylenyl)ethanone

All these compounds possess musky notes of varied strength andsubstantivity, with character differences which can be more or lessmarked. Their specific odor properties are described in detail in thecontext of the respective preparation examples appearing further on.

In addition, the synthesis of compounds (I) can lead to mixtures ofcompounds a) and b), or c) and d), or e) and f). Such mixtures werefound to be perfectly adequate for use in perfumery applications.

One can further rite, as preferred compounds the mixtures of thefollowing compounds i) and j) or k) and l):

i)2,3,3a,4,5,9b-hexahydro-5,5,8,9b-tetramethyl-1H-benz[e]indene-7-carbaldehyde

j)2,3,3a,4,5,9b-hexahydro-5,5,7,9b-tetramethyl-1H-benz[e]indene-8-carbaldehyde

k)1-(2,3,3a,4,5,9b-hexahydro-5,5,8,9b-tetramethyl-1H-benz[e]inden-7-yl)-1-ethanone

l)1-(2,3,3a,4,5,9b-hexahydro-5,5,7,9b-tetramethyl-1H-benz[e]inden-8-yl)-1-ethanone.

The odor properties of these mixtures are also described in detail inthe corresponding preparation examples.

As previously cited, the process of the invention allows the preparationof these compounds via the use of new starting products, obtainedaccording to original techniques. In spite of the prior art knowledgerelated to the synthesis of musky aromatic compounds, that of thecompounds (I) tuned out to present specific problems in so far as itinvolved the preparation of sterically hindered molecules.

The process of the invention comprises the previously described stepsand starts from novel hydrocarbons of formula ##STR18## wherein a)indexes m and n define identical integer numbers equal to zero, symbolsR⁵ and R⁸ represent each a methyl radical, symbols R⁶ and R⁷ can beidentical or different and represent each a hydrogen atom or a methylradical, and either symbol R⁴ represents a methyl radical, symbols R'and R" are identical and stand each for a methyl radical and symbol R³represents a hydrogen atom or a methyl radical, or symbol R⁴ designatesa methyl radical, symbol R" a hydrogen atom and symbols R' and R³ each amethyl radical, or R³ and R⁴ are identical and designate each amethylene radical belonging to a ring such as indicated by the dottedline and R' and R" designate respectively a hydrogen atom and a methylradical, with the proviso that the following combination is excluded:

1. R³ ═R⁴ ═CH₂ and R⁶ or R⁷ ═CH₃ ;

or wherein

b) indexes m and n are different and define each an integer number equalto 0 or 1, symbols R' and R" represent respectively a hydrogen atom anda methyl radical, symbol R³ stands for a hydrogen atom, symbol R⁴ for amethyl radical and, either symbols R⁵ and R⁶ are identical (n=1) andstand each for a methylene group belonging to a ring such as representedby the dotted line, symbol R⁷ designating a hydrogen atom and symbol R⁸a methyl radical, or R⁵ designates a methyl radical and R⁶ a hydrogenatom, R⁷ and R⁸ being then identical (m=1) and standing each for amethylene radical belonging to a cycle such as represented by the dottedline,

or from a mixture of two or more structural isomers of formula (III).

Hydrocarbons (II) can be converted into the desired compounds of formula(I) following methods which involve a combination of reactions of theabove-mentioned type. Several combinations of such reactions can be usedto prepare the compounds of formula (I) but one or another of saidcombinations will be preferred, depending on the structure of thedesired final product.

Thus, when compounds of formula (Ia) or (Ib) are to be prepared, onewill typically use a starting hydrocarbon of formula (III), which willbe preferentially treated as represented in the following reactionscheme: ##STR19## Aldehydes of structure (Ia) cart be separated from theobtained mixture by the usual separation techniques such as, forexample, gas chromatography. These aldehydes can also be converted intothe corresponding ketones of formula (Ib) through alkylation in thepresence of CH₃ Li in ether, followed by hydrolysis and oxidation of theresulting alcohol, for example by means of pyridinium chlorochromate indichloromethane.

The starting products of formula (IIIa) can be prepared from benzenederivatives following a multistep process represented in Scheme II andwhich resorts to the use of a combination of reactions of the typedescribed by T. F. Wood and P. O. Roblin [see, for example, T. F. Woodet al., J. Org. Chem. 28, 2248 (1963)] but which requires the use ofnovel reagents: ##STR20##

Typically, the Lewis acid used in the alkylation reaction will bealuminium trichloride and, the Grignard reagent used in the followingstep, CH₃ MgI. The cylisation reaction is an acid catalyzed reaction,typically by H₂ SO₄. The ethyl ethers used in the alkylation step arenovel compounds which are obtained as described in detail in thepreparation examples presented further on.

We observed that compounds of formula (IIIa) wherein R⁶ ═R⁷ ═H could beprepared more advantageously by an original process, illustrated in thefollowing reaction scheme: ##STR21##

It consists of a reaction sequence comprising the coupling of twohalides, followed by an intramolecular alkylation, in acidic medium,which has the advantage of avoiding the use of a Lewis acid. Inaddition, it is a cheaper process, which also produces less residues.

In the case of the synthesis of compounds (II), and more particularlythat of the mixtures containing the two isomeric forms of thesecompounds already cited, we discovered that one could use preferentiallythe process represented in. Scheme IV leading directly to mixtures ofthe appropriate precursors (IIIb1.) and (IIIb2.): ##STR22##

The first step in this process consists in a Grignard reaction(hydrometallation) starting from isoprene and pivaloyl chloride(t-BuCOCl, Bu=butyl). This is an original approach which replacesadvantageously the Friedel-Crafts acylation generally used to obtain theketone illustrated in Scheme IV. A classical Friedel-Crafts alkylationfollows and, then, reduction by means of LiAlH₄. Alternatively, thislast step could have been replaced by a hydrogenation reaction. Thefinal step in the process represented is a cyclization which can becarried out under varied conditions. However, the relative proportion ofdiastereoisomers (IIIb1.) and (IIIb2.) in the mixture obtained in thiscyclization is strongly dependent on the conditions of the latter. Forinstance, we discovered that the production of isomer (IIIb1.) could befavored by the use of polyphosphonic acid (PPA) or P₂ O₅ (see Example4).

The synthesis represented in Scheme IV makes it possible to preparesymmetrical hydrocarbons wherein the two methyl groups substituting thebenzene ring are equivalent, said hydrocarbons being then oxidized withCe (IV) to yield a mixture of aldehydes of formula (II) which can beseparated by gas chromatography. The mixture of the correspondingketones can then be obtained by conventional reactions, as is describedin Example 6 presented further on.

The Ce (IV) oxidation reaction can actually be applied in a general wayto other hydrocarbons of formula (III). This reaction is carried out inmethanol and can lead to the formation of an intermediate acetal, thehydrolysis of which provides the corresponding aldehyde.

The synthesis of tricyclic compounds of formulae (Ie) to (Ih) wasachieved starling from tricyclic hydrocarbons (IIIc) and (IIId). Thelatter can be prepared by the following processes, which resort to asophisticated combination of conventional reactions, illustrated belowand carried out under the conditions described in detail in thecorresponding preparation examples presented later on: ##STR23##

Hydrocarbon (IIIc) is converted into aldehyde (Ie) and ketone (Ig) byway of Friedel-Crafts acylation reactions. Likewise, mixtures ofcompounds of formula (If) and (Ih) were obtained starting from themixture of hydrocarbons (IIId). The specific conditions of thesetransformations are described in detail in Examples 7 to 10.

The invention will now be described in further detail by way of thefollowing preparation examples, wherein temperatures are indicated indegrees centigrade and the abbreviations have the meaning common in theart.

Example 1 Preparation of5,6,7,8-tetrahydro-1,3,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde andof 5,6,7,8-tetrahydro-3,4,5,5,8-hexamethyl-2-naphthalenecarbaldehyde

a) Preparation of1,2,3,4-tetrahydro-1,1,4,4,5,6,7-heptamethylnaphthalene

In a 3 l three-neck flask, equipped with a mechanical stirrer and keptunder nitrogen, 426.0 g of methallyl chloride were slowly (2 h) added toa mixture of 1,2,3-trimethylbenzene (1582.0 g) and H₂ SO₄ (84.0 g) whilethe temperature was maintained at 20°. After 3 h, the H₂ SO₄ wasdecanted and the organic phase was washed with, in succession, water, anaqueous solution saturated with NaHCO₃ and an aqueous solution saturatedwith NaCl. The excess of 1,2,3-trimethylbenzene (1100.0 g) was recoveredthrough distillation (70°/9.31×10³ to 2.66×10³ Pa) and the residue wasdistilled (97°-100°/2.66 Pa). A mixture (726.0 g) of two isomers(A/B≈4:0:60) was obtained which gave the following analytical data andwas used as such in the next reaction.

A. 1-(2-chloro-1,1-dimethylethyl)-3,4,5-trimethylbenzene

IR(CDCl₃): 2950, 1485, 1390 cm⁻¹

NMR(¹ H,60 MHz): 1.38(s,6H); 2.13(s,3H); 2.27(s,6H); 3.59(s,2H);7.01(s,2H) δ ppm

MS: 210(M⁺,8), 174(7), 161(100), 133(28), 121(34), 115(14), 105(16),91(19), 77(14).

B. 1-(2-chloro-1,1-dimethylethyl)-2,3,4-trimethylbenzene

IR(CDCl₃): 2950, 1485, 1390 cm⁻¹

NMR(¹ H,60 MHz): 1.50(s,6H); 2.17(s, 3H); 2.27(s,3H; 2.38(s,3H);3.82(s,2H); 6.96(d,J=8 Hz, 1H); 7.13(d,J=8 Hz, 1H) δ ppm

MS: 210(M⁺,10), 174(12), 161(100), 133(56), 121(34), 115(19), 105(22),91(27),77(19).

In a 1.51 flask equipped with a mechanical stirrer and kept undernitrogen, a suspension of Mg (41.0 g) in THF (tetrahydrofuran, 100 ml)was heated to reflux. 10 ml of a solution of the mixture of (A+B)prepared above (300.0 g) in THF (100 ml) were then added. Once thereaction had started, more THF was added (300 ml) and then the remainingsolution of (A+B) in THF was added over 75 min. The reaction mixture wasstirred for 30 min at a temperature of 75°. Methallylchloride (193.0 g)was then added over 20 min, while maintaining the reaction mixture atreflux. During this introduction, MgCl₂ was seen to precipitate, themixture having become heavier, but without hindering the stirring. After30 min, the mixture was cooled to 10° and hydrolized with water (400ml). The phases were separated and the aqueous layer was extracted withether. The-combined organic layers were washed with an aqueous solutionsaturated NaCl, and the solvents were evaporated. Distillation(130°-135°/2.66×10² Pa) provided 294.0 g (yield 90%) of a colorless oilymixture whose NMR spectrum (¹ H, 60 MHz) showed a large singlet at 4.65δ ppm. This mixture was directly used in the following cyclizationreaction. In a 500 ml three-neck flask equipped with mechanical stirringand kept under nitrogen, 288.0 g of the above-mentioned oily mixturewere added to a mixture of petroleum ether 30°-50° (100 ml) and H₂ SO₄(7.0 g), over 1 h and at a temperature of 5°-10°. After 30 min at 10°,the H₂ SO₄ was separated from the organic layer and the latter waswashed successively with H₂ O, saturated NaHCO₃ solution and saturatedNaCl solution. Recrystallization of the raw product in ethanol (1.11)provided 240.0 g (yield 83%) of1,2,3,4-tetrahydro-1,1,4,4,5,6,7-heptamethylnaphthalene.

M.p. 79°-82°

IR(CDCl₃): 2920, 1455, 1395, 1380 cm⁻¹

NMR(¹ H,60 MHz): 1.27(s,6H); 1.41(s,6H); 1.65(s,4H; 2.12(s,3H);2.27(s,3H); 2.38(s,3H); 7.01(s,1H) δ ppm

MS: 230(M⁺,22), 216(15), 215(100), 174(11), 173(73), 171(14), 159(41),141(10), 128(10), 57(16).

b) In a flask equipped with a mechanical stirrer, a condenser and anitrogen inlet, 6.25 g of1,2,3,4-tetrahydro-1,1,4,4,5,6,7-heptamethylnaphthalene prepared in a)were dissolved in 70 ml of CCl₄ and 5.56 g of NBS (N-bromosuccinimide)were added to the solution. The suspension was irradiated with a 100 Wlamp to bring the reaction mixture to reflux. After 45 min, thetemperature was allowed to return to room temperature and the reactionmixture was poured on H₂ O and extracted thrice with ether. The combinedorganic layers were washed with an aqueous solution saturated with NaCl,dried over Na₂ SO₄, filtered and the solvents evaporated.

The raw mixture thus obtained (10.5 g) was composed of the three bromidederivatives of benzene (see Scheme I) and contained about 15% by weightof unreacted starting naphthalene derivative, owing to the fact that thereaction had not been completed in order to avoid the formation ofdibromides. This raw mixture was then dissolved in N-methylpyrrolidone(70 ml) and H₂ O (10 ml) and heated to reflux for 1 h. After cooling to20°, the reaction mixture was extracted with ether. The organic layerwas washed with water three times, then with an aqueous solutionsaturated with NaCl, dried over Na₂ SO₄ and the solvents wereevaporated. 7.65 g of raw product were obtained, which were submitted tocolumn chromatography on SiO₂ (200 g), using as elution agent a mixtureof cyclohexane/ether 98:2, giving an apolar fraction containing5,6,7,8-tetrahydro-2,3,5,5,8,8-hexamethyl-1-naphthalenemethanol (1.3 g)and a polar fraction containing isomers5,6,7,8-tetrahydro-1,3,5,5,8,8-hexamethyl-2-naphthalenemethanol and5,6,7,8-tetrahydro-3,4,5,5,8,8-hexamethyl-2-naphthalenemethanol (1.86 g,respectively 80:20). The combined yield of these two fractions was 3.16g (47% in alcohols).

In a 100 ml three-neck flask equipped with a magnetic stirrer, athermomether and a nitrogen inlet, 2.18 g of PCC (pyridiniumchlorochromate) were dissolved in methylene chloride (15 ml) and asolution of the above-mentioned polar fraction (1.55 g, 4:1) inmethylene chloride (5 ml) was added dropwise, while maintaining thetemperature at 20°. Two hours later, the reaction mixture, which hadbecome dark brown, was filtered on SiO₂ (20 g) with CH₂ Cl₂ and thesolvent was evaporated. Recrystallization from methanol provided 501 mgof a mixture which contained5,6,7,8-tetrahydro-1,3,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde and5,6,7,8-tetrahydro-3,4,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde, ina relative portion of 9 to 1, and 439.0 mg of mother liquors (containing85% of the above-mentioned aldehydes). The yield of therecrystallization fraction and the mother liquor in the above-citedmixture was 57%.

A sample of5,6,7,8-tetrahydro-3,4,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde,containing 10% of5,6,7,8-tetrahydro-1,3,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde, wasobtained by preparative chromatography. The analytical data from thesecompounds is presented hereinafter.

Treatment of5,6,7,8-tetrahydro-2,3,5,5,8,8-hexamethyl-1-naphthalenemethanol (1.30 g)with PCC, in an analogous way to that described above, afforded 456.0 mcg of 5,6,7,8-tetrahydro-2,3,5,5,8,8-hexamethyl-1-naphthalenecarbaldehyde (M.p. 74°-80°) and mother liquors(476.0 g, 80% pure), with an estimated yield of 61%. The analytical datafrom this product is also described hereinafter.

5,6,7,8-tetrahydro-1,3,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde

IR(CDCl₃): 2975, 2940, 2850, 1685, 1600, 1385 cm⁻¹

NMR(¹ H,360 MHz): 1.30(s,6H); 1.45(s, 6H); 1.68(broad s,4H); 2.47(s,3H);2.70(s,3H); 7.07(s,1H); 10.58(s,1H) δ ppm

MS: 244(M⁺,50), 229(100), 187(19), 173(22), 159(56), 145(13), 128(10)

Odor note: nicely musky, dearly ambrette (seeds).

5,6,7,8-tetrahydro-3,4,5,5,8,8-hexamethyl-2-naphthalenecarbaldehyde

IR(CDCl₃): 2975, 2940, 2850, 1685, 1600, 1385 cm⁻¹

NMR(¹ H,360 MHz): 1.33(s,6H); 1.47(s, 6H); 1.68(s,4H); 2.42(s,3H);2.53(s,3H); 7.67(s,1H); 10.26(s,1H) δ ppm

MS: 244(M⁺,50), 229(100), 187(19), 173(22), 159(56), 145(13), 128(10)

Odor note: musky.

5,6,7,8-tetrahydro-2,3,5,5,8,8-hexamethyl-1-naphthalenecarbaldehyde

IR(CDCl₃): 2990, 2955, 2890, 1705, 1470, 1380 cm³¹ 1

NMR(¹ H,360 MHz): 1.28(s,6H); 1.36(s,6H); 1.61-1.72(m,4H); 2.16(s,3H);2.26(s,3H); 7.20(s,1H); 10.83(s,1H) δ ppm

MS: 244(M⁺,23), 229(100), 211(40), 196(18), 185(15), 169(17), 159(29),141(17), 128(15), 115(15).

c) 5,6,7,8-tetrahydro-1,3,5,5,8,8-hexamethyl-2-naphthalenecarbaldehydewas also selectively prepared from 1,2,3,4-tetrahydro-1,1,4,4,5,7-hexamethylnaphthalene. The latter was obtained following a preparationmethod analogous to that described in a), using as starting productsm-xylene (490.9 g), methallyl chloride (150.0 g) and H₂ SO₄ (30.0 g),their reaction having yielded 182.8 g (yield 56%) of1-(2-chloro-1,1-dimethyl)-2,4-dimethylbenzene (containing 10% of itsregioisomer). 100.0 g of the latter compound were then treated under theconditions described in a) to yield 97.0 g (yield 88%) of1-(1,1,4-trimethyl -4-pentenyl)-2,4-dimethylbenzene. The cyclization ofthe latter product (86.9 g) yielded 0.6 g (yield 93%) of1,2,3,4-tetrahydro-1,1,4,4,5, 7-hexamethylnaphthalene.

B.p.: 120°/2.66×10³ Pa

IR: 2910, 1600, 1455, 1390, 1375 cm⁻¹

NMR(¹ H,60 MHz): 1.24(s,6H); 1.35(s, 6H); 1.66(s,4H); 2.23(s,3H);6.75(broad s,1H); 7.00(broad s,1H) δ ppm

MS: 216(M⁺,33), 201(100), 159(67), 145(29), 141(13), 128(11), 115(10).

A mixture of 1,2,3,4-tetrahydro-1,1,4,4,5,7-hexamethylnaphthalene (5.0g) of TiCl₄ (7.32 g) in methylene chloride (40 ml) was treated with Cl₂CHOCH₃ (2.66 g) in methylene chloride (5 ml), at 0° and over 20 min. Thetemperature of the reaction mixture was allowed to reach 20° (20 min)and said mixture was then poured on ice water and extracted with ether.The organic phase was successively washed with a 10% aqueous solution ofNaOH, water and an aqueous solution saturated with NaCl, then dried overNa₂ SO₄, evaporated and recrystallized from methanol. 4.06 g (yield 72%)of 5,6,7,8-tetrahydro -1,3,5,5,8,8-hexamethyl-2-naphthalenecarbaldehydewere obtained, the product being identical in data to that described inb).

Example 2 Preparation of5,6,7,8-tetrahydro-1,3,5,5,6,8,8-heptamethyl-2-naphthalenecarbaldehydeand of5,6,7,8-tetrahydro-3,4,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

a) Preparation of ethyl 3,4-dimethyl-4-pentenoate

In a 2 l flask equipped with a mechanical stirrer and kept undernitrogen, a solution of tiglic acid (100.0 g) in sulphuric ether (300ml) was added to a suspension of LiAlH₄ (28.5 g) in ether (300 ml) over3 h, the temperature having been kept at 5°. The reaction mixture wasmade to reflux for 1 h and then left under stirring, at roomtemperature, for one night. After cooling with an ice bath, 100 ml of 5%HCl were added dropwise, followed by 600 ml of 15% HCl and 200 ml ofether to avoid agglomeration. The reaction mixture was extracted withsulphuric ether (3×400 ml) and the combined extracts were washed, insuccession, with a saturated solution of NaCl (3×50 ml), 10% Na₂ CO₃ (20ml) and H₂ O. The organic phases were collected together, dried over Na₂SO₄ and evaporated to concentrate (40°/9.7×10⁴ Pa). The residue (84.8 g)was fractionated in a Vigreux column under normal vacuum to yield 59.3 g(yield 69% ) of 2-methyl-2-buten-1-ol.

In a 3 l flask equipped with a mechanical stirrer and a condenser, keptunder nitrogen, a mixture of triethylorthoacetate (1117.8 g), propionicacid (2.3 g) and 2-methyl-2-buten-1-ol (59.3 g) was heated at 118° for72 h in order to distil the ethanol gradually as it was formed. Theexcess of triethylorthoacetate was recovered and the distillation wascompleted under reduced pressure. The raw product thus obtained (69.0 g)contained around 80% of the desired pentenoate. Purification on aFischer column yielded 43.7 g (41%) of ethyl 3,4-dimethyl-4-pentenoate.

b) Preparation of ethyl3,4-dimethyl-4-(3,4,5-trimethyl-1-phenyl)pentanoate

In a flask equipped with a mechanical stirrer, a thermometer, anintroduction ampoule and maintained under nitrogen, 52.0 g of ethyl3,4-dimethyl-4-pentenoate prepared as in a) were added dropwise, over 1h, to a suspension of AlCl₃ (115.04 g) in 1,2,3-trimethylbenzene (359.99g), while keeping the temperature at 0°-5°. Once the introduction wascompleted, the temperature was allowed to increase to 20° and, 15 minlater, the reaction mixture was poured on icy water. The mixture wasextracted with ether and washed successively with 5% NaOH, water and aNaCl saturated solution. It was then dried over Na₂ SO₄, filtered andthe solvents were evaporated. The excess of 1,2,3-trimethylbenzene wasdistilled at 70°/2.66×10³ Pa. Distillation of the residue at160°/2.66×10² Pa provided 70.23 g (yield 76%) of ethyl3,4-dimethyl-4-(3,4,5-trimethyl-1-phenyl)-pentanoate.

IR: 2970, 1740, 1455, 1380, 1305, 1190 cm⁻¹

NMR(¹ H,60 MHz): 0.85(d,J=7 Hz,3H); 1.23(t,J=7 Hz,3H); 1.23(s,6H);≈1.80(m,1H); ≈2.20(m,2H); 2.15(s,3H); 2.26(s,6H); 4.06(q,J=7 Hz,2H);6.93(s,2H) δ ppm

MS: 276(M⁺,3), 231(3), 161(100), 147(8), 133(14), 121(13), 105(7),91(6).

c) Preparation of2,4,5,5-tetramethyl-5-(3,4,5-trimethyl-1-phenyl)-2-pentanol

A 1.5 l sulfuration flask equipped with a condenser and kept undernitrogen was charged with 15.12 g of Mg which were covered withanhydrous ether (20 ml). The Grignard reaction was triggered by adding 5to 10 ml of a CH₃ I (96.56 g) solution in ether (180 ml). As soon as thereaction had started (ether reflux), an ether solution (200 ml) of thepentanoate prepared in b) (69.0 g) was added to the reaction mixture. Wecontinued to add the CH₃ I solution mentioned above while controllingthe ether reflux with a cold water bath (solution added over about 1 h).The mixture was allowed to continue to react for 1 h, the temperaturehaving been kept at 20°, and then carefully hydrolyzed with icy water.It was subsequently extracted with ether, washed with saturated NaCl,dried over Na₂ SO₄, filtered and the solvents were evaporated. 65.1 g(yield≈100%) of the desired alcohol were obtained and used as such inthe following cyclization reaction.

d) Preparation of1,2,3,4-tetrahydro-1,1,2,4,4,5,6,7-octamethylnaphthalene

A 250 ml three-neck flask equipped with a mechanical stirring and keptunder N₂, was charged with 100 g of 90% H₂ SO₄, to which a solution ofthe raw alcohol obtained in c) (65.1 g) in petroleum ether 80°-100° (≈50ml) was added dropwise (1 h), while the temperature was kept between 0°and 10°. Once the introduction was completed, the temperature wasallowed to increase to 20° and, 30 min later, the H₂ SO₄ was decantedand ice water was added to the reaction mixture (≈300 ml). The latterwas extracted with ether, washed with 10% NaOH and saturated NaCl, driedover Na₂ SO₄, filtered and evaporated. Recrystallization of the rawproduct in ethanol afforded 37.3 g of1,2,3,4-tetrahydro-1,1,2,4,4,5,6,7-octamethylnaphthalene and 18.77 g ofmother liquors containing around 55% of this same compound. Thiscompound was used as the starting product in the synthesis of thedesired aldehydes.

IR(CDCl₃): 2920, 1455, 1385, 1360 cm⁻¹

NMR(¹ H,60 MHz): 0.94(d,J=7 Hz,3H); 1.10(s,3H); 125(s,3H); 1.39(s,3H);1.43(s,3H); 1.60-1.90(m,3H); 2.11(s, 3H); 2.23(s,3H); 2.36(s,3H);7.07(s,1H) δ ppm

MS: 244(M⁺,30), 229(100), 187(92), 173(73), 156(16), 141(17), 128(12),115(11), 57(13), 41(14).

e) The method described in Example 1b) was followed (Scheme 1)

In the halogenation reaction, the following reagents were used: NBS(28.82 g), 1,2,3,4-tetrahydro-1,1,2,4,4,5,6,7-octamethylnaphthalene[prepared in d), 35 g] and CCl₄ (350 ml). After the usual treatment,54.1 g of raw product were obtained, consisting in the mixture of benzylbromides and unreacted starting octamethylnaphthalene. This rawproduct/54.1 g) was used in the hydrolysis reaction withN-methyl-pyrrolidone (300 ml) and H₂ O (45 ml). After the usualtreatment, 44 g of raw product were obtained, containing5,6,7,8-tetrahydro-3,4,5,5,7,8,8-heptamethyl-2-naphthalenemethanol,5,6,7,8-tetrahydro-1,3,5,5,6,8,8-heptamethyl-2-naphthalenemethanol and5,6,7,8-tetrahydro-2,3,5,5,6,8,8-heptamethyl-1-naphthalenemethanol, aswell as 15% of unreacted1,2,3,4-tetrahydro-1,1,2,4,4,5,6,7-octamethylnaphthalene.

This mixture (44.0 g, ≈77% weight of alcohols) was used in the oxidationreaction, with PCC (44.9 g) and CH₂ Cl₂ (300 ml). After the filtration,two fractions were obtained, one containing 5.22 g of theabove-mentioned octamethylnaphthalene and the other 11.8 g of a mixturecomposed of5,6,7,8-tetrahydro-1,3,5,5,6,8,8-heptamethyl-2-naphthalenecarbaldehyde,5,6,7,8-tetrahydro-3,4,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehyde,and5,6,7,8-tetrahydro-2,3,5,5,6,8,8-heptamethyl-1-naphthalenecarbaldehyde,in the respective proportions of 4:5:1 (yield over 3 steps 27%).Preparative chromatography afforded a 9:1 mixture of the first twoaldehydes cited.

5,6,7,8-tetrahydro-1,3,5,5,6,8,8-heptamethyl-2-naphthalenecarbaldehyde

IR(CDCl₃): 2920, 1680, 1595, 1460, 1370 cm⁻¹

NMR(¹ H,360 MHz): 0.99(d,J=7 Hz,3H); 1.16(s,3H); 1.28(s,3H); 1.35(dd,J=14.2 Hz,1H); 1.42(s,3H); 1.48(s,3H); 1.67(t,J=14 Hz,1H); 1.86(m,1H);2.49(s,3H); 2.72(s,3H); 7.12(s,1H); 10,61(s,1H) δ ppm

MS: 258(M⁺,35), 245(95), 201(47), 187(60), 173(100), 159(35), 141(20),128(17), 115(13), 91(13), 57(18), 41(15).

5,6,7,8-tetrahydro-3,4,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

IR(CDCl₃): 2920, 1680, 1595, 1460, 1370 cm³¹ 1

NMR(¹ H,360 MHz): 2.43(s,3H); 2.52(s,3H); 7.73(s,1H); 10.61(s,1H) δ ppm

MS: 258(M⁺,35), 245(95), 201(47), 187(60), 173(100), 159(35), 141(20),128(17), 115(13), 91(13), 57(18), 41(15)

Odor note: this mixture possessed a nice musky note, dean but slightlyweak.

Example 3 Preparation of5,6,7,8-tetrahydro-1,3,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehydeand5,6,7,8-tetrahydro-3,4,5,5,6,8,8-heptamethyl-2-naphthalenecarbaldehyde

a) Preparation of ethyl 2,4-dimethyl-4-pentenoate

In a 3000 ml flask mechanically stirred and equipped with a condenserand a N₂ inlet, a solution of sodium ethylate (46.0 g Na, 700 mlabsolute ethanol) was prepared and 286.0 g of ethyl acetoacetate addedthereto, over 30 min, at a temperature of 15°. The mixture was stirredfor 30 min at room temperature and 182.0 g of β-methallyl chloride wereadded to it all at once, at the same temperature. Stirring wasmaintained for 50 h and the mixture was then refluxed for 1 h. Thesodium chloride precipitate was filtered and the filtrate wasconcentrated by solvent evaporation. Ther residue (402.6 g) wasfractionated on a Vigreux column, then on a column filled with glasshelices topped by a total reflux head. 161.4 g of ethyl2-acetyl-4-methyl-4-pentenoate were used in the following reaction.

A 2000 ml flask, equipped with mechanical stirring, a condenser and N₂atmosphere, was charged with 24.3 g of Na and 400 ml of ethanol toprepare sodium ethylate. After cooling to 15°, the pentenoate previouslyprepared (161.4 g) was added to the solution over 30 min, whilemaintaining the temperature at 15°-20°. 15 g of methyl iodide were addedin one go. The exothermic reaction was controlled with an ice bath tokeep the temperature at 30° for around 90 min. Stirring was continuedduring 2 h 30 at 20° and the mixture was then taken to reflux for 4 h.The reaction mixture was left at rest for 56 h and then the NaIprecipitate was filtered. 700 ml of toluene were added and the mixturewas filtered again. 700 ml of toluene/ethanol azeotrope (rotavapor,74°/6×10⁴ Pa) were distilled and 250 ml of the distillate were added tothe residue. After cooling to 5°, a new filtration was done. Thefiltrate was evaporated (74°/2.7×10⁴ Pa). 240.3 g of raw product werethus obtained, which were purified on a Vigreux column, and then in aglass helix column topped by a total reflux head. 78.1 g of pure ethyl2-acetyl-2,4-dimethyl-4-pentenoate were thus obtained and this productwas used in the following reaction.

b) Preparation of ethyl 2,4-dimethyl-(3,4,5-trimethyl-1-phenyl)pentanoate

The method described in Example 2b) was followed with the reagents citedhereinafter. AlCl₃ (125.2 g), 1,2,3-trimethylbenzene (390.9 g), ethyl2,4-dimethyl-4-pentenoate [prepared in a), 56.5 g]. After usualtreatment and distillation, 81.9 g of the desired product were obtained(B.p. 160°/2.7×10² Pa, yield 82%).

IR: 2950, 1730, 1450, 1370, 1180, 1150 cm⁻¹

NMR(¹ H,60 MHz): 1.02(d,J=7 Hz,3H); 1.14(t,J=75 Hz,3H); 1.24(s,6H);≈1.70(m,2H); 2.12(s,3H); 2.27(s,6H); ≈3.0-3.5(m,1H; 3.91(q,J=7.5 Hz,2H); 6.93(s,2H) δ ppm

MS: 276(M⁺,6), 231(5), 187(5), 161(100), 133(11), 121(10), 105(5).

c) Preparation of2,3,5,5-tetramethyl-5-(3,4,5-trimethyl-1-phenyl)-2-pentanol

We followed the method described in Example 2c), using the followingreagents: Mg (17.7 g), MeI (108.9 g), ethyl2,4-dimethyl-(3,4,5-trimethyl-1-phenyl)pentanoate [prepared according tob), 81.5 g], ether (650 ml). 82.0 g of raw product were obtained andthis product was used as such in the cyclization reaction that followed.

d) Preparation of1,2,3,4-tetrahydro-1,1,2,4,4,6,7,8-octamethylnaphthalene

We followed Example 2d) with the reagents cited hereinafter: raw alcoholprepared in c) (82 g), 90% H₂ SO₄ (100 g), petroleum ether (≈50 ml).After crystallization, 50 g of the desired pure product were obtainedand 24.3 g of mother liquors containing around 60% of same product(overall yield 68%). The latter was used as starting product in thesynthesis of the desired aldehydes.

IR(CDCl₃): 2950, 1450, 1380, 1360 cm⁻¹

NMR(¹ H,60 MHz): 1.01(d,J=7 Hz,3H); 1.24(s,3H); 1.26(s,3H); 1.33(s,3H;1.47(s,3H); ≈1.70(m,3H); 2.15(s,3H); 2.26(s,3H); 2.41(s,3H); 7.00(s,1H)δ ppm

MS: 244(M⁺,30), 229(85), 187(100), 173(58), 157(10).

e) The method described in Example 1b) was followed (Scheme I).

In the halogenation reaction, the following reagents were used: NBS(38.29 g), 1,2,3,4-tetrahydro-1,1,2,4,4,5,6,7-octamethylnaphthalene[prepared in d), 50.0 g], CCl₄ (400 ml). After 45 min, the usualtreatment was carried out to give 54.2 g of raw product containing themixture of benzyl bromides and ≈15% by weight of unreactedoctamethylnaphthalene.

This raw product (54.2 g) was mixed with N-methylpyrrolldone (300 ml)and water (45 ml). The hydrolysis reaction afforded 39.1 g of rawproduct containing5,6,7,8-tetrahydro-1,3,5,5,7,8,8-heptamethyl-2-naphthalenemethanol,5,6,7,8-tetrahydro-3,4,5,5,6,8,8-heptamethyl-2-naphthalenemethanol and5,6,7,8-tetrahydro-2,3,5,5,7,8,8-heptamethyl-1-naphthalenemethanol, aswell as about 15% by weight of unreacted starting octamethylnaphthalene.

The latter raw product (39.1 g, ≈83% by weight of alcohols) was used inthe oxidation reaction, together with 44.9 g of PCC and 300 ml of CH₂Cl₂. After filtration, two fractions were obtained, one containing 6.02g of starting octamethylnaphthalene and the other containing 5.0 g of amixture of the three aldehydes mentioned above. Gas chromatographyallowed the separation of pure 5,6,7,8-tetrahydro-1,3,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehyde and a sample of5,6,7,8-tetrahydro-3,4,5,5,6,8,8-heptamethyl-2-naphthalenecarbaldehydecontaining 10% by weight of the preceding compound.

IR (mixture,CDCl₃): 2950, 2920, 1680, 1580, 1455, 1360 cm⁻¹

5,6,7,8-tetrahydro-1,3,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

NMR(¹ H,360 MHz): 1.01(d,J=7 Hz,3H); 1.25(s,3H); 1.30(s,3H); 1.35(s,3H;1.46(s,3H); ≈1.40(m,1H); 1.64(t,J=13 Hz,1H); 1.79(m,1H); 2.47(s,3H);1.32(s,3H; 7.05(s,1H); 10.60(s,1H) δ ppm

MS: 258(M⁺,27), 243(38), 201(41), 187(55), 173(100), 159(32), 143(43),128(25), 115(25), 105(24), 91(35), 77(21), 57(23), 43(24).

5,6,7,8-tetrahydro-1,3,5,5,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

NMR(¹ H,360 MHz): 1.02(d,J=7 Hz,3H); 1.28(s,3H); 1.32(s,3H); 1.35(s,3H);1.47(s,3H); ≈1.40(m,1H; 1.64(t,J=13 Hz,1H); 1.82(m,1H; 2.44(s,3H);2.54(s,3H; 7.66(s,1H); 10.27(s,1H) δ ppm

MS: 258(M⁺,27), 243(38), 201(41), 187(55), 173(100), 159(32), 143(43),128(25), 115(25), 105(24), 91(35), 77(21), 57(23), 43(24)

Odor note: this mixture presented a very musky, animal, burnt note.

Example 4 Preparation oftrans-5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

a) Preparation of 2,2,4,5-tetramethyl-5-hexen-3-one

A 1 l flask equipped with a mechanical stirrer, a thermometer and acondenser, maintained under nitrogen, was charged at 20° with,successively, recently distilled isoprene (30.0 g), PrMgBr [(Pr=propyl,1.88N, 213 ml; prepared from PrBr (Pr=propyl) (54.2 g), Mg (12.7 g) and(CH₃ CH₂)₂ O (200 ml)], and C_(p2) TiCl₂ (Fluka, 1 g). After 15 h at20°, the solution was transferred via canula into a cooled 1.5 l flask(-10°) containing pivaloyl chloride (53.0 g) in solution in (CH₃ CH₂)₂ O(100 ml). After stirring for 1 h, the mixture was poured on saturatedNH₄ Cl, extracted with ether and the organic layers were washed with 5%NaOH, H₂ O and saturated NaCl. They were then dried over Na₂ SO₄,filtered and evaporated under vacuum. 49.2 g of a yellow liquid werethus obtained. The desired ketone was distilled on a bridge(50°/1.33×10³ Pa). 39.2 g (yield 61%) of2,2,4,5-tetramethyl-5-hexen-3-one (96% pure).

IR(CDCl₃): 3050, 1700, 1640, 1470, 1360, 990 cm⁻¹

NMR(¹ H,60 MHz): 4.80(s,2H); 3.71(q,J=7 Hz,1H); 1.74(broad,3H); 1.17(d,J=7 Hz,3H); 1.12(s,9H) δ ppm

MS: 154(M⁺,3), 85(32), 69(14), 57(100), 41(34).

b) Preparation of5-(3,4-dimethyl-1-phenyl)-2,2,4,5-tetramethyl-3-hexanone

A solution of the ketone prepared in a) (37.2 g) in o-xylene (50 ml) wasadded dropwise to a suspension of AlCl₃ (36.2 g) in o-xylene (380 ml)over 1 h while maintaining the temperature at 0°. The temperature wasallowed to increase to 10° (around 30 min) and the reaction mixture waspoured on H₂ O, extracted with ether and washed with Na₂ CO₃, thensaturated NaCl. After drying over Na₂ SO₄ and concentrating bydistillation on a bridge, 54.4 g of the desired ketone were obtained(97% pure, yield 88%).

B.p. ≈120°/1.33×10² Pa

IR(CDCl₃): 2950, 1690, 1470, 1360, 990 cm⁻¹

NMR(¹ H,60 MHz): 7.05(broad,3H); 3.27(q,J=7 Hz,1H); 2.26(s,3H);2.22(s,3H); 1.46(s,3H); 1.37(s,3H); 0.96(s,9H; 0.95(d,J=7 Hz,3H) δ

MS: 260(M⁺,1), 147(100), 131(8), 119(17), 91(10), 57(12), 41(10).

c) Preparation of5-(3,4-dimethyl-1-phenyl)-2,2,4,5-tetramethyl-3-hexanol

In a 1 l flask equipped with mechanical stirring, a thermometer and acondenser, maintained under nitrogen, a solution of the ketone preparedin b) (54.4 g) in (CH₃ CH₂)₂ O (50 ml) was added to a suspension ofLiAlH₄ (3.80 g) in (CH₃ CH₂)₂ O (250 ml). After cooling to 10°, 4 ml ofwater were carefully added dropwise, then 4 ml of 5% NaOH and 12 ml ofwater. The resulting alcohol was filtered, concentrated and distilled(bridge: 130°-140°/2.0×10² Pa). 31.5 g of the desired product wereobtained (98% pure; yield 97%; mixture of diastereomers 94:6).

IR: 3600, 2980, 1840, 1370, 1010 cm⁻¹

NMR(¹ H,360 MHz+D₂ O): 7.18(s,1H); 7.14(broad d,J=7.5 Hz,1H);7.07(d,J=7.5 Hz,1H); 3.09(d,J=7.5 Hz,1H); 2.04(s,3H); 2.02(s,3H);2.01(q,J=7 Hz,1H); 1.46(s,3H); 1.20(s,3H); 1.05(d,J=7 Hz,3H); 0.81(s,9H)δ ppm

MS: 244(trace, M⁺,18), 187(7), 173(7), 147(100), 131(8), 119(17),107(9), 91(10), 57(8), 41(13).

d) Preparation of trans-1,2,3,4-tetrahydro-1,1,2,3,4,4,6,7-octamethylnaphthalene andcis-1,2,3,4-tetrahydro-1,1,2,3,4,4,6,7-octamethylnaphthalene

The alcohol prepared under c) (41.6 g) was added under stirring andexternal cooling to a mixture of methanesulphonic acid (21.25 g) and P₂O₅ (8.5 g). The temperature was kept at 40° for 4 h. The reactionmixture was cooled, rendered more fluid by adding CH₂ Cl₂ (10 ml) andtransferred into a 1 l beaker containing an ice-water mixture. Thehydrocarbon formed in the reaction was extracted with ether, washed with5% NaOH, H₂ O, then saturated NaCl, dried over Na₂ SO₄ and concentrated.37.3 g of raw product, containing a mixture of trans- and cis- isomersin the respective proportions of 3:1, were obtained. Crystallizationfrom ethanol, distillation of the mother liquors (110°/1.33×10² Pa) andcrystallization of the distilled fractions provided 16.7 g of thedesired trans- isomer (98% pure, yield 43%) and an oil containing amixture of trans- and cis- isomers (19.8 g, ≈56% pure, trans/cis≈40:60).Residues: 0.52 g.

trans-1,2,3,4-tetrahydro-1,1,2,3,4,4,6,7-octamethylnaphthalene

IR(CHCl₃): 2990, 1500, 1450, 1400, 1370 cm⁻¹

NMR(¹ H,360 MHz): 7.12(s,2H); 2.23(s,6H); 1.58(m,2H); 1.31(s,6H);1.09(s,6H); 0.96(d,J=6 Hz,6H) δ ppm

NMR(¹³ C,360 MHz): 143.1(s); 133.6(s); 128.2(d); 39.5(d); 37.5(s);29.6(q); 25.7(q); 19.5(q); 13.9(q) δ ppm

MS: 244,(M⁺,7), 229(24), 187(43), 173(100), 157(12), 145(23), 128(11),91(8) 57(38), 41(9).

cis-1,2,3,4-tetrahydro-1,1,2,3,4,4,6,7-octamethylnaphthalene

IR(CHCl₃): 2990, 1500, 1450, 1400, 1370 cm⁻¹

NMR(¹ H,360 MHz):7.08(s,2H); 2.23(s, 6H); 1.88(broad q,2H); 1.26(s,6H);1.25(s,6H); 0.95(d,J=7 Hz,6H) δ ppm

NMR(¹³ C,360 MHz): 142.0(s); 133.6(s); 127.9(d); 41.4(d); 37.1(s);33.7(q); 27.7(q); 19.4(q); 13.3(q) δ ppm

MS: 244(M⁺,7), 229(24), 187(43), 173(100), 157(12), 145(23), 128(11),91(8) 57(38), 41(9).

e) To a solution of trans-1,2,3,4-tetrahydro-1,1,2,3,4,4,6,7-octamethylnaphthalene [obtained in d), 16.0 g] in methanol (700 ml)were added 16 portions of Ce(NH₄)₂ (NO₃)₆ (16×16.0 g=256.0 g) inmethanol (16×100 ml), over 8 h, while maintaining the temperature at50°. Around 2/3 of the methanol were evaporated and the resultingproduct was extracted with petroleum ether 30°-50°/sat NaCl. The rawproduct thus obtained (19.1 g) contained a new, heavier product,trans-6-dimethoxymethyl-1,2,3,4-tetrahydro-1,1,2,3,4,4,7-heptamethylnaphthalene,which was hydrolized prior ro crystallization by means of a 5% aq. HClsolution in tetrahydrofuran.

After crystallizing in ethanol, treating the mother liquors andrecrystallizing, 12.1 g of the desiredtrans-5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthalenecarbaldehyde(98.5% pure, yield 80%) were obtained.

6-dimethoxymethyl-1,2,3,4-tetrahydro-1,1,2,3,4,4,7-heptamethylnaphthalene

IR: 2960, 2880, 2840, 1440, 1360, 1100, 1070, 1050, 980 cm⁻¹

NMR(¹ H,360 MHz, CDCl₃): 0.94-0.96(d,6H,J=7 Hz); 1.09(s,3H); 1.10(s,3H);1.30(s,3H); 1.32(s,3H); 1.53-1.60(m, 2H); 2.32(s,3H); 3.36(s,3H);5.38(s,1H); 7.11(s,1H); 7.48(s,1H) δ ppm

NMR(¹³ C,90.5 MHz,CDCl₃): 145.54(s); 142.65(s); 132.72(s); 129.16(d);125.25(d); 102.72(d); 53.51(q); 53.30(q); 39.43(d); 39.33(d); 37.61(s);37.58(s); 29.59(q); 29.45(q); 25.51.(q); 18.52(q); 13.80(q) δ ppm

MS: 304(3), 273(49), 243(18), 201(42), 187(51), 173(23), 159(19),131(20), 75(100), 57(32), 43(15).

trans-5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

IR(CDCl₃): 2960, 1680, 1600, 1430, 1360, 1203 cm⁻¹

NMR(¹ H,360 MHz): 10.19(s,1H); 7.80(s,1H); 7.91(s,1H); 2.61(s,3H);1.59(m,2H); 1.35(s,3H); 1.33(s,3H); 1.12(s,6H); 0.99(d,J=6 Hz,6H) δ ppm

MS: 258(M⁺,24), 243(58), 201(30), 187(100), 173(40), 159(34), 141(18),131(23), 115(15), 57(12), 43(47).

Odor note: described in the introduction of this specification.

Example 5 Preparation ofcis-5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthalenecarbaldehyde

This product, which is a diastereomer of the compound prepared inExample 4, was obtained via oxidation of a mixture containing the twohydrocarbon, isomers prepared according to Example 4d), followed bypreparative chromatography.

IR(CDCl₃): 2960, 1680, 1600, 1450, 1360, 1205 cm⁻¹

NMR(¹ H,360 MHz): 10.20(s,1H); 7.76(s,1H); 71.8(s,1H); 2.62(s,3H);1.92(m,2H); 1.32(s,3H); 1.31(s,3H); 1.28(2s,6H); 0.95(d,J=7 Hz,6H) δ ppm

NMR(¹³ C): 192.7(d); 151.3(s); 143.0(s); 137.2(s); 132.2(s); 131.3(d);130.2(d); 41.1(d); 41.1(d); 38.0(s); 37.4(s); 33.7(q); 33.4(q); 27.6(q);27.4(q); 19.2(q); 13.2(q); 13.2(q) δ ppm

MS: 258(M⁺,24), 243(58), 201(30), 187(100), 173(40), 159(34), 141(18),115(15), 57(12), 43(47).

Odor note: musky, earthy, slightly animal.

Example 6 Preparation oftrans-(5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthyl)-1-ethanone

A solution of CH₃ MgCl/THF (9.7 ml, 3.54N) was added to a solution, inTHF (40 ml), of the aldehyde prepared in example 4 (7.0 g), whilekeeping the temperature at 20° (ice bath). The reaction mixture washydrolized with NH₄ Cl, extracted with ether and washed with H₂ O andsaturated NaCl. It was then dried over Na₂ SO₄ and concentrated. 6.9 gof raw product were obtained. A solution of 6.26 g of this product inCH₂ Cl₂ (60 ml) was added dropwise to a solution of PCC (7.86 g) in CH₂Cl₂ (20 ml). The mixture was stirred for 2 h keeping the temperature at20°, filtered over SiO₂ under a slight pressure of nitrogen,concentrated (5.86 g) and crystallized in ethanol. The mother liquorswere chromatographed (SiO₂, CH₂ Cl₂) and crystallized. A total amount of4.3 g oftrans-(5,6,7,8-tetrahydro-3,5,5,6,7,8,8-heptamethyl-2-naphthyl)-1-ethanone(95% pure, yield 62%) was obtained.

IR(CDCl₃): 2960, 1670, 1440, 1350, 1220 cm⁻¹

NMR(¹ H,360 MHz,CDCl₃): 7.73(s,1H); 7.20(s,1H); 2.45(s,3H); 2.40(s,3H);1.58(m,2H); 1.30(s,6H); 1.06(s,6H); 0.91(d,J=6.5 Hz,6H) δ ppm

MS: 272(M⁺,7), 257(22), 215(14), 201(40), 173(23), 159(16), 141(16),128(17), 115(12), 57(13), 41(100).

Odor note: described in the introduction to this specification.

Example 7 Preparation of1,2,6,7,8a-hexahydro-3,6,6,8a-tetramethyl-4-acenaphthylcarbaldehyde

a) Preparation of ethyl 2-acetyl-3-(2-methyl-1-phenyl)propanoate

In a 2.5 l flask equipped with a mechanical stirrer, a condenser, athermometer and a nitrogen inlet, α-chloro-o-xylene (Fluka, 140.6 g) wasmixed with ethyl acetoacetate (130 g), a fine powder of potassiumcarbonate (414 g) and 800 ml of toluene. The mixture was heated to 100°for 20 h. After cooling, H₂ O was added (500 ml). The organic phase waswashed with water and saturated NaCl, then dried over Na₂ SO₄ andevaporated. 269.6 g of a brown oil were obtained which was distilled(120°-125°/5.65 Pa) to yield 163 g of ethyl2-acetyl-3-(2-methyl-1-phenyl) propanoate (98% pure, yield 70%).

b) Preparation of 4-(2-methyl-1-phenyl)-2-butanone

An autoclave of 1 l was charged with 161.5 g of ethyl2-acetyl-3-(2-methyl-1-phenyl)propanoate obtained in a), 16.4 g of NaCl,150 ml of DMSO and 25 ml of H₂ O. The mixture was heated to 160° for 7h. The cooled reaction mixture was extracted with petroleum ether30°-50°, washed times with a saturated solution of NaCl, dried over Na₂SO₄, filtered and evaporated. Distillation of the obtained raw product(13.3 Pa) provided 101 g of the desired butanone (98% pure, yield 91%).

P. Eb. 65°-70°/13.3 Pa

IR: 2925, 1705, 1490, 1350, 1160 cm⁻¹

NMR(¹ H,60 MHz): 2.10(s,3H); 2.28(s, 3H); 2.65-3.00(m,4H); 7.07(s,4H) δppm

MS: 162(M⁺,2), 144(100), 129(50), 119(52), 105(83), 91(45), 77(28),65(18), 43(58).

c) Preparation of 7-(2-methyl-1-phenyl)-2,5-dimethylhept-3-yne-2,5-diol

In a 1 l flask 2-methyl-3-butyn-2-ol (47 g) was added to a solution ofEtMgBr (1.12 mol of Mg and 1.12 mol of ethyl bromide in 200 ml ofanhydrous ether at reflux) over 30 min while keeping the temperature at0°-5°. The heterogeneous mixture was heated to 20° for 30 min, understirring, and then to reflux for 1 h. 69.7 g of4-(2-methyl-1-phenyl)-2-butanone prepared according to b) were added andthe reaction mixture was heated to reflux for 1 h. The mixture, by thenhomogeneous, was hydrolized with an aqueous solution saturated with NH₄Cl and ice, extracted with ether, washed with saturated NaCl, dried andevaporated. 107.9 g (yield≈100%) of a yellow oil, consisting of thedesired diol, were obtained.

IR: 3350 cm⁻¹

NMR(¹ H,60 MHz): 1.50(s,9H); 1.70-2.03(m,2H); 2.30(s,3H);2.63-2.94(m,2H); 2.94(broad s,2H); 7.13(s,4H) δ ppm.

d) Preparation of 7-(2-methyl-1-phenyl)-2,5-dimethylheptane-2,5-diol

60 g of the diol prepared in c) were hydrogenated in an autoclave, at70° and 50 H₂ atmospheres, in the presence of about 3.0 g of Raney-Ni inmethanol (80 ml). After 4 days under the same conditions, the suspensionwas filtered and the filtrate evaporated to obtain 60 g of7-(2-methyl-1-phenyl)-2,5-dimethylheptane -2,5-diol (yield≈100%).

IR: 3350, 2930, 1455, 1370 cm⁻¹

NMR(¹ H,60 MHz): 1.22(2s,9H); 1.60(s,4H); 1.50-1.90(m,2H); 2.22(broad s,2H, exchange with D₂ O); 2.30(s,3H); 2.45-2.85(m,2H); 7.12(s,4H) δ ppm.

e) Preparation of1,2,2a,3,4,5-hexahydro-2a,5,5,8-tetramethylacenaphthene

A stirred and cooled (4°) solution of the diol prepared in d) (12.5 g)in 1,2-dichloroethane (150 ml) was treated dropwise with TiCl₄ (16.5ml). After stirring for 30 min, an aqueous solution saturated with NaCl(50 ml) was added dropwise, the temperature rising to 30°. The mixturewas washed with an aqueous solution saturated with NaHCO₃, then with anaqueous solution saturated with NaCl, dried over Na₂ SO₄, evaporated anddistilled (130°/2.66 Pa). 7.76 g of the desired product were thusobtained (yield 77%).

IR: 2920, 1485, 1445, 1360 cm⁻¹

NMR(¹ H,360 MHz): 1.12(2s,6H); 1.38(s,3H); 1.60-1.85(m,4H); 2.02(m,2H);2.22(s,3H); 2.68(m,1H); 2.97(m,1H); 6.94(d,J=8 Hz,1H); 7.01 (d, J=8Hz,1H) δ ppm

MS: 214(M⁺,15), 199(100), 157(18), 143(14).

f) The precursor 1,2,2a,3,4,5-hexahydro-2a,5,5,8-tetramethylacenaphtheneobtained according to e) was treated in a way similar to that describedin example 1c), with TiCl₄ and Cl₂ CHOCH₃. 4.71 g of said precursor wereused in the acylation reaction and 3.14 g of1,2,6,7,8,8a-hexahydro-3,6,6,8a-tetramethyl-4-acenaphthylenecarbaldehyde(yield 59% ).

IR(CDCl₃): 2950, 2855, 1680, 1590, 1450 cm⁻¹

NMR(¹ H,60 MHz): 1.15(s,6H); 1.41(s, 3H); 1.65-2.30(m,6H); 2.52(s,3H);2.70-3.15(m,2H); 7.60(s,1H); 10.23(s,1H) δ ppm

MS: 242(M⁺,18), 27(100), 199(20), 165(10), 157(36), 143(25), 128(17),115(14), 92(12), 69(11).

Odor note: nicely musky with a relatively weak musk-ambrette side

Example 8 Preparation of(1,2,6,7,8,8a-hexahydro-3,6,6,8a-tetramethyl-4-acenaphthylenyl)-1-ethanone

A solution of the hydrocarbon prepared in example 7e) (1.28 g) in1,2-dichloroethane was added dropwise to a suspension of AlCl₃ (960 mg)in 1,2-dichloroethane (10 ml). To the orange suspension 518 g of acetylchloride were added. After 30 min, water was added and the reactionproduct was extracted with ether. The organic phase was washed with asaturated solution of NaHCO₃, then with a saturated solution of NaCl,dried over Na₂ SO₄, evaporated and purified by column chromatography(SiO₂, cyclohexane/ethyl acetate 95:5). 0.80 g of the desired ketonewere obtained (yield 52%).

IR(CHCl₃): 2920, 2850, 1675, 1445, 1345, 1290, 1245 cm⁻¹

NMR(¹ H,60 MHz): 1.13(s,3H); 1.15(s, 3H); 1.40(s,3H); 1.58-1.85(m,4H);1.98-2.09(m,2H); 2.37(s,3H); 2.56(s,3H); 2.74(m,1H); 2.99(m,1H);7.43(s,1H) δ ppm

MS: 256(M⁺,11), 241(87), 199(20), 153(10), 43(100).

Odor note: musky with a character typical of the nitro-aromatic muskycompounds.

Example 9 Preparation of a mixture of2,3,3a,4,5,9b-hexahydro-5,5,8,9b-tetramethyl-1H-benz[e]indene-7-carbaldehydeand 2,3,3a,4,5,9b-hexahydro-5,5,7,9b-tetramethyl-1H-benz[e]indene-8-carbaldehyde

a) Preparation of methyl 1-(2-methyl-2-propenyl)-2-oxo-1-cyclopentanecarboxylate

A mixture of methyl 1-cyclopentanone-2-carboxylate (Fluka, 106.5 g),methallyl chloride (88 ml), K₂ CO₃ (207 g) and acetone (500 ml) washeated to reflux for 2 h. More methallyl chloride (44 ml) was added andthe mixture was refluxed for 20 h. The white reaction mass was dissolvedin water and the product extracted with ether. Washing (3% aqueous NaOH)and the usual treatment provided 148 g of an oil which was submitted toa fractional distillation to give 113 g of the desired ketoester (yield77%, B.p. 105°-107°/5.32×10² Pa).

IR: 2950, 1750, 1720, 1430, 1210 cm⁻¹

NMR(¹ H,60 MHz): 1.64(s,3H); 1.70-3.00(m,8H); 3.68(s,3H); 4.73(broads,1H); 4.85(broad s,1H) δ ppm

MS: 178(M⁺,16), 168(16), 140(45), 136(30), 121(36), 109(100), 93(35),79(60), 67(36), 55(41), 39(33).

b) Preparation of 2-(2-methyl-2-propenyl)-1-cyclopentanone

A mixture of the keto-ester prepared in a) (78.4 g), HMPA(hexamethylphosphoramide, 250 ml) and LiCl (34 g) was heated to 73° for36 h. Extraction (3 times, ether/water) of the reaction product provided70.3 g of a brown oil which was submitted to fractional distillation togive 34.7 g of the above-mentioned ketone (yield 62%, B.p.63°-75°/5.32×10² Pa).

NMR(¹ H,60 MHz): 1.71(s,3H); ≈1.50-2.70(m,9H); 4.68(broad s,2H) δ ppm

MS: 138(M⁺,45), 123(12), 110(38), 95(37), 82(100), 67(77), 55(38),41(35).

c) Preparation of a mixture of2-[2-methyl-2-(4-methyl-1-phenyl)propyl]-1-cyclopentanone and2-[2-methyl-2-(3-methyl-1-phenyl)propyl]-1-cyclopentanone 10.35 g of theketone prepared in b) were added dropwise to a suspension of AlCl₃ (15g) in toluene (138 g) at -20°. The temperature was allowed to raise to10° and the reaction mixture was stirred for 30 min, hydrolized withwater and extracted with ether. Part (6 g) of the yellow oil thusobtained (16.56 g, yield 95%) was distilled in a bulb-to-bulb apparatus(130°/1.33 Pa) to give 5.2 g of a 3:1 mixture of the above-cited ketones(yield 83%).

IR: 2950, 1735, 1510, 1450, 1150 cm⁻¹

NMR(¹ H,60 MHz, characteristic peaks): 1.28(s,6H); 2.30(large s,3H);6.90-7.30(m,4H) δ ppm

MS: 133(M⁺,100), 105(25), 91(10), 41(12).

d) Preparation of a mixture of1-methyl-2-[2-methyl-2-(4-methyl-1-phenyl)propyl]-1-cyclopentanol and1-methyl-2-[2-methyl-2-(3-methyl-1-phenyl)propyl]-1-cyclopentanol

A solution of CH₃ MgI (prepared with 3.4 ml of CH₃ I and 1.2 g of Mg) inether (100 ml) was treated at 20° with a solution of the raw mixture ofketones obtained in c) (10.44 g) in ether (10 ml). Once the addition wascompleted (about 10 min), the resulting mixture of alcohols washydrolized and extracted with ether. It was then used as such in thefollowing preparation step.

e) Preparation of a mixture of1-[1,1-dimethyl-2-(2-methyl-1-cyclopenten-1-yl)ethyl]-4-4-methylbenzeneand1-[1,1-dimethyl-2-(2-methyl-1-cyclopenten-1-yl)ethyl]-3-methylbenzene

A solution of the raw alcohol mixture obtained in d) (9.84 g), petroleumether 30°-50° (150 ml) and 98% H₂ SO₄ (0.75 ml) was stirred for 1 hwhile keeping the temperature at 20°. The reaction mixture was extractedand bulb-to-bulb distilled (130°/5.65 Pa) to give 6.89 g of a mixturecontaining the above-mentioned olefins.

NMR(¹ H,60 MHz, characteristic peaks): 1.25(s,6H); 1.54(broad s,3H);2.29(broad s,3H); 6.88-7.30(m,4H) δ ppm

f) Preparation of a mixture of1,2,3,3a,4,5-hexahydro-1a,5,5,8-tetramethylacenaphthylene and1,2,3,3a,4,5-hexahydro-1a,5,5,7-tetramethylacenaphthylene

A solution of olefine mixture obtained in e) (5.5 g), petroleum ether30°-50° (120 ml) and 98% H₂ SO₄ (0.5 ml) was heated to reflux (50°) for5 h. Extraction and bulb-to-bulb distillation (140°/13.3 Pa) provided amixture of the above-mentioned hydrocarbons.

NMR(¹ H,60 MHz,characteristic peaks): 1.20-1.30(4s,9H); 2.30(s,3H);6.80-7.30(m,3H) δ ppm

g) The acylation reaction of the hydrocarbons prepared in f) was carriedout as described in Example 1c) using TiCl₄ (1.86 ml) in methylenechloride (30 ml) and Cl₁₂ CHOCH₃ (0.8 ml) in methylene chloride (5 ml).1.05 g of a mixture of the isomers2,3,3a,4,5,9b-hexahydro-5,5,8,9b-tetramethyl-1H-benz[e]indene-7-carbaldehydeand 2,3,3a,4,5,9b-hexahydro-5,5,7,9b-tetramethyl-1H-benz[e]inde, in therelative proportions of 3:1, was obtained (yield 45%).

IR: 2940, 2850, 1680, 1600, 1340, 1440, 1205 cm⁻¹

NMR(1H,60 MHz): 1.22-1.42(4s,9H); 1.40-2.30(m,9H); 2.62(s,3H);7.10(7.17*)(s,1H); 7.70(7.64*)(s,1H); 10.14(s,1H) δ ppm

* minor isomer's peaks

MS: major isomer--256(M⁺,29), 241(100), 199(11), 185(45), 171(58),157(45), 143(28), 128(22), 69(24)

MS: minor isomer--256(M⁺,57), 241(100), 227(37), 214(23), 199(27),185(57), 171(100), 157(57), 143(38), 128(35), 115(23), 69(28), 55(26),41 (28).

Odor note: musky, floral.

Example 10 Preparation of a mixture of1-2,3,3a,4,5,9b-hexahydro-5,5,8,9b-tetramethyl-1H-benz[e]indene-7-yl)-1-ethanoneand1-(2,3,3a,4,5,9b-hexahydro-5,5,7,9b-tetramethyl-1H-benz[e]inden-8-yl)-1-ethanone

This ketone mixture was obtained from the hydrocarbon mixture preparedin Example 9f) and following a method analogous to that described inExample 8. A mixture of the isomeric ketones above-mentioned (0.45 g) inthe relative proportions of 3:1, was obtained.

NMR(¹ H,60 MHz): 1.19-1.34(5s,9H); 1.40-2.30(m,9H); 2.49 and 2.53(2s+2shoulders,6H); 7.03(7.06*)(s,1H); 7.60(7.53*)(s,1H) δ ppm

* minor isomer's peaks

MS: 270(M⁺,13), 255(43), 213(8), 199(8), 185(8), 171(7), 153(8), 141(8),128(10), 115(10), 91(8), 43(100).

Odor note: musky, fruity.

What we claim is:
 1. A compound of:a.6-dimethoxymethyl-1,2,3,4-tetrahydro-1,1,2,3,4,4,7-heptamethylnaphthalene; b.cis-6-dimethoxymethyl-1,2,3,4-tetrahydro-1,1,2,3,4,4,7-heptamethylnaphthalene;orc.trans-6-dimethoxymethyl-1,2,3,4-tetrahydro-1,1,2,3,4,4,7-heptamethylnaphthalene.